CHAPTEE XIII 



0L1G0CHAETA (EARTHWORMS AND THEIR ALLIES) 



INTRODUCTION ANATOMY REPRODUCTION BIONOMICS DISTRI- 

 BUTION CLASSIFICATION MICRODRILI AND MEGADRILI 



The Oligochaeta form a well-marked branch of that exceedingly 

 large assortment of animals vaguely spoken of as worms, and 

 embracing a number of types many of which have no near 

 relationship to each other. From this great and unnatural 

 group, which has survived as " Vermes " even in some quite 

 modern text-books, we can separate off those forms which show 

 a plain segmentation or division of the body internally as well 

 as externally into a series of more or less similar rings, as 

 a Class Chaetopoda. This Class, consisting of the Orders 

 mentioned on p. 241, includes the worms which form the 

 subject of the present chapter the Oligochaeta, as they were 

 originally called by Grube, on account of the fewness of their 

 chaetae as compared with the number possessed by the majority 

 of the Polychaeta. 



Our knowledge of this group, as of so many others, dates from 

 Aristotle, who called the earthworms the " intestines of the earth/' 

 But it is only very recently that the numerous and remark- 

 able genera of exotic earthworms have been anatomically 

 investigated ; indeed the common British species was not 

 really well known before the publication of the memoirs of 

 Lankester 1 and Claparede 2 in 1864 and 1868, in spite of the 

 elaborate quarto devoted to it by Morren, 3 the botanist, in 18 26. 



1 Quart. J. Micr. Sci. (n.s.) vol. iv. 1864, p. 258 ; and v. pp. 7, 99. 



'-' Zeitschr. iciss. Zool. xix. 1869, p. 563. 



3 Dc Lumbrici tcrrestris Historia naturali, Brussels, 1S29. 



